Convection Oven

ABSTRACT

A convection oven having a vapor collection system; water injection system; easily accessible electrical components; and a variable-speed, reversible blower is disclosed. The vapor collection system collects vapor from the cooking chamber during a cooking event, condenses the vapor, and drains the condensed vapor. The water injection system injects water for impact against a blower wheel for dispersion into the air circulating through the cooking chamber. The electrical components are housed within a housing that in a closed position conceals the components and in a closed position exposes the components for easy access. The rotational speed and direction of the variable-speed, reversible blower is controlled during a cooking event according to predetermined speed curves which may include one or more reversal events to achieve more uniform cooking of food. A main controller is programmable via an operator input (e.g., liquid crystal display touch screen) to control operating parameters of the oven.

CROSS-REFERENCE TO RELATED CASES

This application is a continuation application claiming priority fromU.S. patent application Ser. No. 12/841,393, filed Jul. 22, 2010, whichclaims priority to PCT Patent Application No. PCT/US2009/032251, filedJan. 28, 2009, which claims priority to U.S. Patent Application No.61/024,095 (provisional), filed Jan. 28, 2008, all of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention generally relates to ovens and more particularlyto a forced-air convection oven for baking bread products, among otherthings.

BACKGROUND OF THE INVENTION

Certain types of food products are especially difficult to cook quicklyand uniformly. Bread is one such product. For proper cooking, the insideof the dough needs to be completely baked while the crust uniformlybrowns to the desired color. Conventional bread-baking ovens havevarious drawbacks.

For example, conventional ovens do not provide convenient access toelectrical components of the ovens for servicing or other purposes.Typically, a control panel or other part must be disassembled to accesselectrical parts. Further, once disassembly enables access to theelectrical components, the components are not mounted within the oven ina position or orientation for convenient servicing. Thus, there exists aneed for an oven that provides convenient access to electricalcomponents of the oven having the components mounted in a position andan orientation conducive to servicing of the components.

Another drawback of known ovens is that steam formed during the bakingprocess is not disposed of in a desirable or efficient manner. Someovens simply expel the steam into the atmosphere surrounding the oven(e.g., inside the baking room or restaurant). Other ovens expel thesteam through an exhaust that leads to the outside atmosphere. Someovens provide a self-contained steam condensing system, but a moreefficient self-contained system is needed.

Drawbacks also exist in the steam generation systems used to injectwater against heated rotating blower wheels to generate steam for thecooking process in existing ovens. For example, some water injectionsystems involve atomizers having complex designs in combination with theblower wheel to atomize injected water. Other water injection systemsare simpler, but result in less efficient generation of steam. Further,in some water injection systems, some of the injected water does notturn to steam and subsequently contacts the product to be cooked (e.g.,bread), undesirably affecting the cooking process. Thus, a simplified,more efficient water injection system is needed.

Finally, conventional convection ovens incorporate various types ofsystems for circulating hot gas (e.g., air) throughout the cookingchamber, including systems having a reversible, variable speed fan.However, such systems often fail to achieve uniform cooking of food inthe cooking chamber.

There is a need, therefore, for an improved oven which meets one or moreof the above needs.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to a convection ovencomprising a cooking chamber for receiving food to be cooked, a blowerfor circulating gas (e.g., air) through the cooking chamber, a heaterfor heating the gas, and a housing for housing electrical components ofthe oven. The housing comprises front, back and side walls. The frontwall is movable from a first position in which the electrical componentsare concealed within the housing to a second position in which theelectrical components are exposed. The electrical components are mountedwithin the housing at positions relative to the front wall such that theelectrical components may be conveniently accessed by an operator whenthe front wall is in the second position. An operator input is providedon the front wall of the housing for inputting information to theelectrical control components.

In another aspect, the oven comprises a cooking chamber for receivingfood to be cooked, a blower for circulating gas (e.g., air) through thecooking chamber, and a heater for heating the gas. The oven alsoincludes a vapor collection system for collecting vapor from the cookingchamber during a cooking event. The vapor collection system comprises acondensing device above the cooking chamber having an inletcommunicating with the chamber for receiving vapor and an outlet fordraining condensed vapor. The condensing device comprises a coilcomprising a plurality of turns configured for gravity feedingcondensate to the outlet.

In another aspect, the oven comprises a cooking chamber for receivingfood to be cooked, a variable-speed, reversible blower for circulatinggas (e.g., air) through the cooking chamber, the blower being operableat more than two speeds when activated, and a heater for heating thegas. The oven also includes a control system comprising an operatorinput and a controller responsive to the operator input for controllingthe rotational speed of the blower during the cooking event according toa predetermined speed curve which includes at least two reversal events.Each reversal event comprises a deceleration of the blower as it rotatesin one direction from a first rotational speed on said speed curve to azero rotational speed, followed by an acceleration of the blower as itrotates in an opposite direction from zero speed to a second rotationalspeed on said speed curve, the second speed being either the same as ordifferent from said first speed. In one embodiment, the shape of thespeed curve is substantially non-linear between the end of one reversalevent and the beginning of another reversal event.

In another aspect, the oven comprises a cooking chamber for receivingfood to be cooked, a variable-speed, reversible blower for circulatinggas (e.g., air) through the cooking chamber, the blower being operableat more than two speeds when activated, and a heater for heating thegas. The oven includes a control system comprising an operator input anda controller responsive to the operator input for controlling therotational speed of the blower during the cooking event according to apredetermined speed curve. In one embodiment, the speed curve has nosubstantial linear components.

The invention is also directed to a method of cooking food in aconvection oven comprising a cooking chamber for receiving food to becooked. The method comprising the steps of placing food in the cookingchamber, and operating a blower of the oven to circulate heated gas(e.g., air) through the cooking chamber to cook the food during acooking event. The operating step comprises controlling the rotationalspeed of the blower during the cooking event according to apredetermined speed curve which includes at least two reversal events.Each reversal event comprises a deceleration of the blower as it rotatesin one direction from a first rotational speed on the speed curve to azero rotational speed, followed by an acceleration of the blower as itrotates in an opposite direction from zero speed to a second rotationalspeed on the speed curve, the second speed being either the same as ordifferent from said first speed. In one embodiment, the shape of thespeed curve is substantially non-linear between the end of one reversalevent and the beginning of another reversal event.

Other objects and features will be in part apparent and in part pointedout hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of an oven of thisinvention;

FIG. 2 is a front elevation of the upper section of the oven of FIG. 1,shown partially in section;

FIG. 3 is an enlarged portion of FIG. 2 showing blower details;

FIG. 4 is a perspective a side wall of the cooking chamber of the uppersection of the oven;

FIG. 5 is an elevation of the side wall of FIG. 4;

FIGS. 6 and 7 show alternative hole patterns in the side wall of FIGS. 4and 5;

FIG. 8 is a perspective a blower wheel of the blower used in the uppersection of the oven;

FIG. 9 is a plan view of the blower wheel;

FIG. 10 is an exploded view of the blower wheel;

FIG. 11 is a view illustrating a water injection system of the uppersection of the oven;

FIG. 12 is a perspective view of the upper section of the oven withparts of a hood removed to show details of a vapor collection system;

FIG. 13 is a perspective of a lower section of the oven;

FIG. 14 is a front elevation of the lower section of the oven of FIG.12, shown partially in section;

FIG. 15 is an enlarged portion of FIG. 14 showing details of a blowerand water injection system in the lower section of the oven;

FIG. 16 is a perspective similar to FIG. 13 but with the door open andthe bottom wall of the cooking chamber removed to show details;

FIG. 16A is an enlarged portion of FIG. 16 showing details of the waterinjection system in the lower section of the oven;

FIG. 17 is an enlarged portion of FIG. 16 showing details of the blowerand water injection system;

FIG. 18 a perspective of a side wall of the cooking chamber of the lowersection of the oven;

FIG. 19 is an elevation of the side wall of FIG. 18;

FIG. 20 is a perspective similar to FIG. 1 but showing a secondembodiment of a vapor collection system on the oven;

FIG. 21 is a perspective of an upper section of the oven of FIG. 20 withparts of the vapor collection system removed to show details and witharrows generally indicating flow of steam and condensate through thevapor collection system;

FIG. 21A is a plan view of the upper section of the oven of FIG. 20 withparts of the vapor collection system removed to show details and witharrows generally indicating cooling air flow over the vapor collectionsystem;

FIG. 22 is a vertical section on line 22-22 of FIG. 21;

FIG. 23 is a perspective of a portion of finned tubing;

FIG. 24 is a wiring diagram;

FIGS. 25A-25E are graphs showing various blower speed and directionprotocols with differing numbers of blower reversal events;

FIGS. 26A-26C are graphs showing various blower speed and directionprotocols with differing frequencies of speed change;

FIG. 27 is a graph showing a blower speed profile for a certain foodproduct;

FIG. 28 is a perspective of a housing for housing electrical componentsof the oven;

FIGS. 29A-29C are sequential perspectives of the housing of FIG. 28showing a wall of the housing moved from a closed position to an openposition;

FIG. 30 is a view similar to FIG. 3 showing an enlarged portion ofanother embodiment of a blower and water injection system;

FIG. 31 is a perspective view a blower wheel of the blower shown in FIG.30;

FIG. 32 is a view illustrating the steam generation/water injectionsystem of FIG. 30;

FIG. 33 is a perspective of another embodiment of the lower section ofthe oven with the door open and the bottom wall of the cooking chamberremoved to show details; and

FIG. 34 is an enlarged portion of FIG. 33 showing details of the blowerand water injection system.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, FIG. 1 illustrates one embodiment of an ovenof this invention, indicated generally by the reference number 1. Theoven is adapted for cooking and baking products such as bread, amongother things, and includes a cabinet, generally designated 5, having anupper section 5A and a lower section 5B. If the oven 1 is used in abread making process, the dough is first proofed in the lower section 5Bof the oven and then baked in the upper section 5A. (As will beunderstood by those skilled in the bread-making field, “proofing” is acontinuation of the process of yeast fermentation which increases thevolume or “rise” of the shaped dough, and an oven used to “proof” breadis often referred to as a “proofer” or “proofer oven.”)

Referring to FIGS. 1-3, the upper section 5A of the oven 5 comprises acooking (e.g., baking) chamber 11 defined by a top wall 13, a bottomwall 15, opposite side walls 17, and a back wall 21. The chamber 11 isaccessible by opening a door 25 which closes the front of the chamber.One or more rack supports 29 are secured to the walls of the chamber forsupporting a number of food racks 33 in the chamber, three such racksbeing shown in FIG. 2. Each rack is sized to hold a number of pans ofbread dough. It will be understood that the number and size of the racks33 can vary without departing from the scope of this invention. Thecooking chamber 11 is surrounded by an upper housing, generallydesignated 41 in FIG. 2, having a top wall 43, a bottom wall 45,opposite side walls 47 and a back wall 51. The top and side walls of thehousing 41 are spaced from respective walls of the cooking chamber 11 toprovide a conduit system or flow path 53 for circulating heated air (orother gas) to, through and from the cooking chamber 11. As shown in FIG.2, the conduit system 53 comprises an upper portion 53 a above thecooking chamber 11 and side portions 53 b at opposite sides of thecooking chamber 11. Other flow path configurations may be used.

A blower, generally indicated at 61 in FIG. 2, is mounted in the upperportion 53 a of the conduit system 53, adjacent the top of the uppersection 5A of the oven, for circulating air (or other gas) through theconduit system. In the illustrated embodiment, air enters the cookingchamber 11 through a plurality of entry openings 65 in the side walls 17of the chamber (FIGS. 4 and 5) and exits the chamber through an exhaustopening 69 in the top wall 13 of the chamber. A heater 71 is providedfor heating the air being circulated. By way of example, the heater maycomprise one or more electric resistance heating elements in the upperportion 53 a of the conduit system 53 located adjacent the top wall 13of the cooking chamber 11. The heater 71 heats the air as it leaves thechamber before it is re-circulated back to the chamber via the conduitsystem. One or more temperature sensors 75 (FIG. 23) are provided in thecooking chamber 11 for sensing the temperature in the chamber andproviding feedback to the control system of the oven. In one embodiment,two temperature sensors 75A, 75B are provided for sensing temperature indifferent zones of the cooking chamber 11. The cooking chamber isilluminated by lights 79 mounted on the back wall of the chamber 11.

Referring to FIGS. 4 and 5, the entry openings 65 in the side walls 17of the cooking chamber 11 are sized and configured for directing heatedair to the food on each rack in the chamber. In general, the numberand/or size of the openings 65 (i.e., the overall air flow area)associated with each rack level increases from the top of the cookingchamber toward the bottom of the chamber to insure that substantiallythe same volume of air is provided to each level of food on the chamber.(Without such an increase in flow area, more heated air would enter thechamber at the upper levels than the lower levels.) The entry openings65 are also configured in shape, size and location to achieve thedesired baking characteristics.

In the particular configuration of FIG. 5, the openings 65 comprisethree distinct patterns, namely, an upper pattern 65A for deliveringheated air to food on the upper rack 33; an intermediate pattern 65B fordelivering heated air to food on the middle or intermediate rack 33; anda lower pattern 65C for delivering heated air to food on the lower rack33. As shown, the upper pattern 65A comprises a first plurality ofrelatively large holes (e.g., 0.312 in.-diameter circular holes) alignedin a horizontal row above the upper rack for directing heated air towardupper portions of the food on the rack, and a first plurality of smallerholes (e.g., 0.125 in.-diameter circular holes) below the larger holesarranged for directing heat toward middle and lower portions of the foodon the upper rack. The intermediate pattern 65B comprises a secondplurality of relatively large holes (e.g., 0.312 in.-diameter circularholes) aligned in a horizontal row above the intermediate rack fordirecting heated air toward upper portions of the food on the rack, anda second plurality of smaller holes (e.g., 0.125 in.-diameter circularholes) below the larger holes arranged for directing heat toward middleand lower portions of the food on the intermediate rack. The lowerpattern 65C comprises a third plurality of relatively large holes (e.g.,0.312 in.-diameter circular holes) aligned in a horizontal row above theupper rack for directing heated air toward upper portions of the food onthe rack, and a third plurality of smaller holes (e.g., 0.125in.-diameter circular holes) below the larger holes arranged fordirecting heat toward middle and lower portions of the food on the lowerrack. It will be observed that the number and location of holes varyfrom pattern to pattern. In general, the arrangement is such that theoverall or total flow area of the openings of the first pattern 65A ofholes is less than the overall or total flow area of the holes in thesecond pattern 65B, and the overall or total flow area of holes of thesecond pattern is less than the overall or total flow area of the holesin the third pattern 65C to provide a more uniform distribution of airto the different levels. The specific configuration (size, shape andlocations) of the holes in the various patterns will vary according tothe size and shape of the food product in the cooking chamber andaccording to the desired qualities of the food after it has finishedbaking. By way of example but not limitation, the openings may becircular holes varying in diameter from 0.060 in. to 1.00 in., or theymay be slots having rounded ends with a size that can range from 0.060in. wide by 0.50 in. long to 0.38 in. wide by 1.5 in. long.

FIGS. 6 and 7 illustrate different entry opening configurations. In FIG.6, the entry openings 85 of each pattern 85A, 85B and 85C are all of thesame size and are arranged in a generally rectangular matrix ofregularly spaced openings extending alongside the food on the racks. Byway of example but not limitation, the openings may be circular holesvarying in diameter from 0.060 in. to 1.00 in., or they may be slotshaving rounded ends with a size that can range from 0.060 in. wide by0.50 in. long to 0.38 in. wide by 1.5 in. long. In FIG. 7, the entryopening patterns 95A, 95B and 95 c each include a single (only one)large opening 95 extending alongside the food on a respective rack 33.It will be observed that the sizes of these openings 95 do not vary.

In one embodiment (FIG. 3), the blower 61 for circulating air throughthe cooking chamber 11 comprises a variable speed, reversible blowermotor 101 mounted in a housing 105 mounted on a top wall 107 of theoven. The blower motor 101 has an output shaft 111 which rotates in abearing 115 about a generally vertical axis 117. The output shaft of themotor 101 is coupled to an input shaft 119 of a blower wheel, generallydesignated 121, located in the upper portion 53 a of the air conduitsystem 53 adjacent (e.g., immediately above) the exhaust opening 69 inthe top wall 13 of the cooking chamber 11. The blower motor 101 isoperable to rotate the blower wheel 121 about the axis of rotation 117to circulate air through the conduit system 53 and cooking chamber 11 atvelocities and flow rates suitable for cooking. Exemplary velocitiesinclude 0-600 ft/min, 10-300 ft/min, and 30-220 ft/min. Rotation of theblower wheel 121 creates suction at the suction side 121 a of the blowerwheel (i.e., the lower portion of the blower wheel adjacent the exhaustopening 69) to pull gas from the cooking chamber 11 through the exhaustopening 69. Gas is expelled from the blower wheel 121 at the output(exhaust) side 121 b of the blower wheel (i.e., the left and right sidesof the blower wheel as shown in FIG. 3) to circulate air through theconduit system 53 to the cooking chamber 11.

In one embodiment, the blower motor 101 is a 230 VAC, 3-phase, 1.2 amp,60 Hz, ⅓ hp induction motor having a speed which is infinitely variableover a range of speeds, e.g., 50-3450 RPM. One such motor is modelnumber P55LVDDB-1405 available from Emerson Electric Company. In anotherembodiment, the motor may have a speed which is variable in smallincrements (e.g., three, four, five, six, seven, eight, nine or tenincrements, or more than ten increments, or more than twenty increments,or more than thirty increments) over a range of speeds. Other variablespeed, reversible motors operable in the same or other speed ranges,voltages or power may also be suitable.

Referring to FIGS. 8-10, the blower wheel 121 is a flat bladed wheelcomprising an upper member 131 which, in the illustrated embodiment,comprises a circular plate (also designated 131), a series of parallelflat blades 135 mounted on the circular plate, and a hub 139 on thecircular plate for receiving the input shaft 119 of the blower wheel.The blades 135 are spaced at equal intervals around the circular plate131 adjacent the periphery of the plate and are oriented in a radialdirection with respect to the axis of rotation 117 of the wheel 121 sothat they lie in generally vertical radial planes relative to the axisof rotation. The blades 135 are secured in position by flanges 145affixed (e.g., spot welded or riveted) to the circular plate 131 and bya lower member 147 which, in the illustrated embodiment, comprises analignment ring (also designated 147), affixed (e.g., spot welded) to theblades. An even or odd number of blades 135 may be used. Other blowerwheel designs may be used.

Referring still to the embodiment illustrated in FIGS. 8-10, at leastone of the blades 135 of the blower wheel 121, and desirably several ofthe blades, comprises a water-dispersion formation 151 for dispersingwater into the cooking chamber 11 in a manner to be described later. Inthis embodiment, each such formation 151 comprises an integral extensionof the blade 135 projecting in a radial direction outward from the bladegenerally in the same radial plane as the blade. The extensions 151 mayhave other shapes without departing from the scope of this invention.

Referring to FIGS. 3 and 11, a water injection system, generallyindicated 171, is provided for delivering water to the blower 61, andspecifically the blower wheel 121, for dispersion into the air conduitsystem 53 and cooking chamber 11. The injection system 171 comprises atleast one injector 173 mounted adjacent the blower wheel 121, and a line177 for supplying water to the injector. A needle valve 181, solenoidvalve 183 and pressure regulator 187 are provided upstream of theinjector for controlling flow to the injector. In one embodiment, thewater injector 173 comprises a 0.25 in. diameter stainless steel tubewith a square-cut end. The components of the injection system 171 may bemounted on a top wall 107 of the oven at a location where the injector173 extends down from the top wall to a position for delivering waterfor impact against the water dispersion formation(s) 151 on the rotatingblades 135 of the heated blower wheel. By way of example, the lower endof the injector may be spaced about 0.5 in. above the dispersionformation(s) 151. As a result, water is dispersed as a fine spray orsteam mist into the air conduit system 53 and heated by the heatingelements 71 to form a vapor (steam) which is carried into the cookingchamber 11 where it settles as a layer on the bread (or other product)to promote the formation of a thin crust which is uniformly browned. Thenumber of injectors 173 can vary.

The injector system 171 is operated to perform a desired number of waterinjection events (e.g., 0-4) during a cooking event. Each such event mayinclude, for example, a number of time-based cycles each comprising arepeat of one second on and two seconds off. Other injectorconfigurations and injection cycles and frequencies are possible.

The cooking chamber 11 and air conduit system 53 is generally a closedsystem in which substantially the same air re-circulates over and overduring a cooking event. As cooler air is heated, as during initialstart-up of the oven, the volume of the air in the conduit system andcooking chamber will increase. To prevent excessive build-up of airpressure inside the cooking chamber, a relief valve 201 is provided torelease air from the conduit system 53 to the atmosphere. An exemplaryrelief valve 201 is shown in FIG. 12. It comprises a short tubularfitting having an inlet end communicating with the air conduit system 53and an outlet end which is closed except for a small opening 205 sizedto provide suitable pressure relief. By way of example, the opening maybe a 0.375-in. diameter opening.

Referring to FIGS. 13-19, the lower (e.g., proofing) section 5B of theoven 1 comprises a second cooking (e.g., proofing) chamber 225 definedby a top wall 227, a removable bottom wall 229, opposite side walls 233,and a back wall 235. The chamber 225 is accessible by opening a door 241which closes the front of the chamber. One or more rack supports 243 aresecured to the walls of the chamber for supporting food racks 251 in thechamber. In this particular embodiment, up to nine racks can be used inthe cooking chamber 225, and each rack is sized to hold a number of pansof bread dough. It will be understood that the number and capacity ofthe racks 251 can vary without departing from the scope of thisinvention. The cooking chamber 225 is surrounded by a housing 261 havinga bottom wall 263 and opposite side walls 265 spaced from respectivewalls of the cooking chamber 225 to provide a conduit system or flowpath 271 for circulating heated air (or other gas) through the cookingchamber. Other flow path configurations may be used.

A blower, generally designated 281 in FIGS. 14-17, is mounted below thebottom wall 229 of the cooking chamber 225 for circulating air (or othergas) through the air conduit system 271 and cooking chamber 225. In oneembodiment, the blower 281 comprises a single speed, single directionblower motor 285 driving a blower wheel 287 positioned in the airconduit system 271 below the bottom wall 229 of the cooking chamber. Theblower wheel 287 rotates about a generally vertical axis 291. In theillustrated embodiment, air enters the cooking chamber 225 through aplurality of entry openings 301 in the side walls 233 of the chamber andexits through an exhaust 305 (FIG. 13) in the bottom wall 229 of thechamber. A heater 311 comprising, for example, one or more electricresistance heating elements heats the circulating air. The heatingelements 311 are located in the air conduit system 271 below the bottomwall 229 of the cooking chamber 225. Other locations are possible. Atemperature sensor 321 (FIG. 24) is provided in the cooking chamber 225for sensing the temperature in the chamber and providing feedback to thecontrol system of the oven. The cooking chamber 225 is illuminated bylights 325 mounted in the chamber, e.g., on the back wall 235 of thechamber.

FIGS. 18 and 19 show an exemplary pattern of entry openings 301 in theside walls 233 of the cooking chamber 225. (Only one side wall 233 isshown, the opposite side wall being essentially identical. However, theopposite wall 233 may have different entry openings 301 to balance airflow to food products within the cooking chamber 225.) The entryopenings 301 are arranged and configured for directing heated air to thefood on the various racks 251. In general, the number and/or size of theopenings 301 (i.e., the overall air flow area of the opening oropenings) associated with each rack level increases from the bottom ofthe cooking chamber 225 toward the top of the chamber to insure thatsubstantially the same volume of air is provided to each level of foodin the cooking chamber 225, in a similar (but inverted) manner asdescribed previously in regard to the entry openings 65 in the uppercooking chamber 11.

In the particular configuration of FIGS. 18 and 19, the entry openings301 are elongate rectangular openings, one such opening extendinghorizontally at each rack level. As will be observed, the height of theopenings 301 gradually increases from the bottom toward the top of theside wall 233, with the uppermost openings 301 having approximately thesame height. Other entry opening configurations are possible. In anyevent, heated air is delivered through these openings 301 and into thecooking chamber 225 at velocities and flow rates which are suitable forthe cooking process being carried out, e.g., a bread proofing process.

A second water injection system, generally indicated 351, is providedfor delivering water to the output (exhaust) side 121 b of the blowerwheel 287 for dispersion into the air conduit system 271 where it isatomized, heated, vaporized and delivered with the heated air to thecooking chamber 225 to promote the cooking (e.g., proofing) process.(See FIGS. 15-17). The water injection system 351 comprises at least oneinjector 355 mounted below the bottom wall 229 of the cooking chambergenerally adjacent the blower wheel 287, although other locations aresuitable. Water is supplied to the injector 355 via a supply line 389. Avalve 391 in the supply line 389 is operable for controlling flow to theinjector 355 (see FIG. 16A). In one embodiment, the water injectionsystem 351 is operated according to a program which can be varieddepending on the particular cooking process being performed in the oven.By way of example, the injector system 351 may be operated to perform anumber of water injection events (e.g., 0-4) during a cooking event,with each such injection event including a number of time-based cycleseach comprising a repeat of one second on and two seconds off. Inanother embodiment, the water injection system 351 is operated accordingto a humidity control system 393 (FIG. 24) comprising a closed loopfeedback control having a humidity sensor 395 mounted within the conduitsystem 271 and controller 397. Humidity detected by the humidity sensor395 is reported to the controller 397. If the humidity is above aspecified high limit, the controller 397 signals the water injectionsystem 351 to deliver less or no water to the conduit system 271 todecrease the humidity. If the humidity is below a specified low limit,the controller 397 signals the water injection system 351 to delivermore water to the conduit system 271 to increase the humidity. Otherinjector configurations and injection cycles and frequencies arepossible.

A vapor collection system, generally indicated at 401, is provided abovethe upper section 5A of the oven (see FIGS. 1 and 12). The system 401comprises a hood generally indicated at 405, having a front portion 407which overhangs the doors 25, 241 of the upper and lower sections 5A, 5Bof the oven, and a rear portion 411 comprising sides walls 413 extendingabove opposite sides of the upper section 5A of the oven. The front andrear portions 407, 411 are separated by a partition 421 having twoexhaust openings 425 therein. An exhaust fan 431 is mounted on top ofthe upper section of the 5A of the oven behind one of the two exhaustopenings 425. (The position of the exhaust fan 431 may vary depending onthe particular installation. In general, it is desirable to mount thefan adjacent the side of the door 25 opposite the hinge to maximize theamount of vapor collected.) Vapor released from the cooking chambers 11,225 when the doors are opened is captured by the front portion 407 ofthe hood and exhausted through one or both of the openings 425 anddirected to a vent 431. In the illustrated embodiment, only one exhaustfan 431 is used, and vapor is exhausted through the opening 425 behindwhich the fan is mounted. The vent is adapted for connection to a flue435 (FIG. 1) communicating with atmosphere either inside or outside thebuilding in which the oven 1 is installed.

FIGS. 20-23 illustrate an alternative vapor collection system, generallydesignated 451, which eliminates the need for a vent and/or flue as inthe previous embodiment. In this system 451, vapor (steam) from thecooking chamber 11 is vented up through a tubular member or other vaporconduit 455 communicating with the chamber 11 to the inlet 457 of asteam condensing device 461 mounted on the top wall 107 of the oveninside an enclosure 465 (e.g., hood). Steam in the cooking chamber 11 isvented up through the conduit 455 as a result of the difference betweenthe pressure inside the cooking chamber 11 and ambient pressure. Noassistance (e.g., a fan or compressed air source) is required to movesteam through the vapor collection system 451. In one embodiment, thesteam condensing device 461 is a condensing coil (also designated 461)comprising a plurality of helical turns 467 which wind down away fromthe inlet 457 for gravity feed of condensate to an outlet 475 of thecondensing device. In the illustrated embodiment, the coil 461 surroundsor wraps around the housing 105 which houses the blower motor 101. Theslope at which the helical turns 467 wind down may be any slopesufficient to cause gravity feed of condensate to the outlet 475, suchas a slope between 1 and 20 degrees. In one embodiment, the slope is a 5degree slope sufficient to cause gravity feed of condensate while alsoaccommodating a 3 to 4 degree out-of-level floor condition. The flow ofsteam and condensate through the coil 461 is generally indicated byarrows in FIG. 21. The outlet 475 communicates with a suitable drain orother collection device 479 for disposal of the condensed liquid.

In one embodiment, the condensing coil 461 desirably comprises finnedtubing. Such tubing may comprise a tube 481 having fins 483 coiledaround and extending radially from the tube, as shown in FIG. 23. Onecondensing coil 461 suitable for this purpose is a coil formed from 1.0in. OD finned stainless steel tubing sold under the trademark Finbraze®by ENF International Inc. of Mobile Ala. Suitable finned tubing can beconstructed by different methods. For example, fins 483 can be brazed tothe tubing 481. Alternatively, the fins 483 can be extruded to thetubing 481 by a cold rotary extrusion process in which continuoushelical fins are radially extruded from aluminum tubing. By way ofexample but not limitation, the condensing coil 461 may comprisestainless steel smooth-bore tubing 481 with copper fins 483. Desirably,such tubing 481 is constructed by extruding copper helical fins 483directly onto the stainless steel tubing. Alternatively, the fins can beextruded as a “sleeve” and heat-expanded to bond to the stainless steeltubing. Several factors must be balanced to accomplish efficient steamcondensation, including the inside diameter of the tubing 481 of thecondensing coil 461, the length of the tubing, the surface area(including fins 483) of the tubing, and the slope of the tubing.

Referring to FIGS. 21 and 21A, one or more fans 485 are mounted on theenclosure 465 for moving relatively cool air into the enclosure throughone or more inlets 487 in the rear wall of the enclosure, along a pathin which the cooling air flows over the cooling coil 461 and out of theenclosure via an exhaust 491. One or more baffles 489 are disposedwithin the enclosure 465 to direct the air flow (generally indicated byarrows in FIG. 21A) to contact substantially the entire surface area ofthe cooling coil 461 (e.g., at least 80 percent of the coil) and toprevent “short circuiting” of the air flow from the inlet 487 to theexhaust 491. As a result, steam in the coil 461 is cooled and condensedinto a liquid which drains through the outlet 475 of the coil to thecollection device 479 for disposal. Louvers 495 are provided in the topwall 107 of the oven for venting hot air which collects between thehousing 41 and the top wall 107 of the oven into the enclosure 465 whereit is also exhausted through exhaust 491. Alternatively, a naturalconvection cooled coil may be used in which the coil is large enoughsuch that sufficient condensation occurs within the coil as a result ofnatural convection cooling, without the fan 485.

Referring to the wiring diagram of FIG. 24, the operation of the oven 1is controlled by a control system 501 comprising, in one embodiment, anoperator input 505, a main controller 507 and a blower speed/directioncontroller 509. In addition to the components described above, thediagram also includes the following components: transformers 521 forreducing the voltage/current to the oven lights 79, 325, main breakerswitches 525, a high-limit thermostat 527 for setting an uppertemperature limit in the cooking chamber 11, a contactor device 531associated with the heater 71 for the cooking chamber 11, and an ovendoor switch 535 which prevents the operation of the blower unless thedoor 25 of the cooking chamber 11 is closed. The electrical componentsof the control system 501 are cooled by cooling fans 541. Alternatively,only one cooling fan 541 may be used.

The operator input 505 comprises suitable input devices (e.g., a touchscreen, switches, buttons, or other devices) mounted on a control panel551 at a convenient location on the oven, such as at the front of theoven between the upper and lower sections 5A, 5B of the oven (see FIG.1). The operator input 505 allows an operator to input for either of thecooking chambers 11, 225 various cooking parameters, instructions and/orother information necessary or desirable for performing a cookingoperation, including the type of food to be cooked, information relatingto the speed and direction of blower operation, number of reversals,desired temperatures, desired humidity, and desired cooking times.

The main controller 507 controls the operation of the heating elements71, 311, the valves 181, 295 of the water injection systems 171, 351,the cooling fans 541, the temperature sensors 75, 321 in the upper andlower cooking chambers 11, 225, the blower 281 in the lower chamber 225,and the humidity control system 393. The main controller 507 also worksin cooperation with the blower controller 509 to control the speed anddirection of the blower 61 circulating air through the upper chamber 11.

In particular, the main controller is programmable via the operatorinput 505 to operate the blower 61 according to a selected protocol toeffect a desired cooking operation in the upper chamber 11. Thisprotocol can be varied depending on the type of food being cooked, thequantity of food being cooked, the desired characteristics to beimparted to such food during cooking (e.g., crispness, extent ofbrowning), and other factors. The main controller is responsive tooperator input to communicate the appropriate blower speed and directioninformation to the blower controller 509 via communication linesdesignated 561 in FIG. 24. The blower controller 509 functions to drivethe blower motor 101 at the desired speeds and in the desired directionor directions to operate the blower wheel 121 in a manner which providesthe desired air flow to the upper cooking chamber 11. One controller 509found to be suitable for this purpose is a programmable controller modelJ7 drive supplied by Yaskawa Electric America, Inc.

Examples of different blower protocols are illustrated in FIGS. 25-27.In general, each blower protocol involves changing the speed of theblower wheel 61 during a cooking event according to a non-linear speedcurve, and optionally effecting one or more reversal events during thecooking event during which the rotational direction of the blower 61 isreversed. It has been found that operating the blower 61 at differentspeeds and periodically reversing its direction causes a correspondingchange in the speed and direction of air circulating through the cookingchamber 11, and that a more uniform baking and browning of the food(e.g., bread) is achieved as a result.

FIG. 25A is a graph showing a blower protocol in which the blower motor101 is operated to rotate the blower wheel 121 during a cooking event ofpredetermined length (e.g., 14 minutes) and at rotational speeds whichincrease and decrease according to the illustrated speed curve 601. Inthis example, the curve resembles a sine wave, and the speed varies froma minimum of rpm of 50 to a maximum rpm of 3450 to circulate air throughthe upper cooking chamber 11 at velocities ranging from a minimumvelocity of less than about 30 ft/min to a maximum velocity of nogreater than about 600 ft/min, and more desirably to a maximum velocityin the range of 220-300 ft/min. Lower or higher speeds and velocitiesmay alternatively be used. The rotational speed change repeats fourtimes during the cooking event, i.e., the frequency is four changes percooking (e.g., baking) event. Further, there are four direction reversalevents occurring at intervals during the cooking event, as representedby the vertical lines 605 on the graph.

Each reversal event is started by a signal from the main controller 507to the blower controller 509 to de-energize the blower motor 101 orotherwise cause it to decelerate as it rotates in one direction from afirst rotational speed on the speed curve 601 to a zero rotationalspeed, followed by an acceleration of the blower motor as it rotates inan opposite direction from zero speed to a second rotational speed onthe speed curve. The second speed may be substantially the same as thefirst speed or substantially different from the first speed, dependingon the shape of the speed curve and the duration of the reversal event.In the latter regard, the duration of each reversal event will depend onthe time it takes the blower wheel 121 to decelerate to zero and then toaccelerate back up to speed in the opposite direction. The duration inone example is no greater than 30 seconds. The duration is moredesirably no greater than 20 seconds, even more desirably no greaterthan 15 seconds, and still more desirably less than 10 seconds. Thereversal events shown in FIG. 25A occur at regular intervals, but theycan also occur at irregular intervals, depending on the desired cooking“recipe” to be followed.

In FIG. 25A, the shape of the speed curve 601 is non-linear between theend of one reversal event and the beginning of another reversal event.Further, the speed of the blower wheel 121 changes constantly orsubstantially constantly during the entire cooking event. That is, thespeed curve is substantially non-linear or, in other words, has nosubstantial linear components. (As used herein, “substantiallynon-linear” and “no substantial linear components” means that the curvehas no linear components lasting more than 45 seconds, or even moredesirably no more than 30 seconds, or even more desirably no more than20 seconds, or even more desirably no more than 10 seconds.) In otherembodiments, the speed curve may have substantial linear components.

FIGS. 25B-25E show four additional blower protocols similar to FIG. 25Aexcept that they include three, two, one and no reversal events,respectively. FIGS. 26A-26C show three additional blower protocolssimilar to FIG. 24 except that the speed change frequencies are five,six and one, respectively. The number of reversal events and thefrequency of speed change can be varied as needed to achieve the desiredbaking results.

FIG. 27 shows a different blower protocol in which the blower 61 isoperated to follow a speed curve 701 in which the blower rotates at asubstantially constant and relatively low speed (e.g., 690 rpm) for apredetermined period (e.g., 80% of the bake event) and then ramps up toa higher speed (e.g., 3450 rpm) for the remainder of the baking event.This type of protocol has been found to be useful for certain foodproducts such as cookies where frozen dough is placed in the baking ovenand cooked. During the process, the dough is heated slowly at the lowerair speeds so that the dough deforms slowly to the proper cookie shape.Once the dough has assumed the proper shape, the blower speed isincreased to bake the dough more rapidly to provide the desiredbrowning.

Other blower protocols may be used. By way of example but notlimitation, the protocols shown in FIGS. 25 and 26 above may be modifiedsuch that the speed of the blower remains constant for one or more dwell(holding) intervals along the speed curve.

As will be described, the desired protocol can be programmed into theoven by the operator using the operator input 505. In particular, theoperator input 505 is configured to enable an operator to select anycombination of one or more of the following: cooking time, cookingtemperature, number of water injection/steam generation events, maximumand minimum blower speed, frequency of speed change, and number ofblower reversal events. In addition, or alternatively, the operatorinput 505 may be configured to enable an operator to select a type offood to be cooked, in response to which the main controller 505automatically selects (i.e., is programmed to select without furtheroperator input) a predetermined speed curve and number of reversalevents for the cooking event.

The control system 501 desirably includes a USB host adapter 821 thatenables connection of a USB memory storage device or flash drive (notshown) for various purposes. For example, end users may import recipesthey have created or retrieved from a website or computer. Further, theUSB host adapter 821 allows for training and maintenance informationstored on a flash drive to be displayed, e.g., on the operator input505, preferably in the form of a liquid crystal display touch screen(also numbered 505) mounted on the control panel 551. Such informationmay include instructions for baking bread or procedures for cleaning theoven 1. Information displayed on the screen 505 may include text,photographs/figures, and video. Maintenance personnel may also use theUSB host adapter 821 to import various operating or firmware updates.

FIGS. 28 and 29 show electrical components of the oven as describedabove housed in a housing 831 located between the upper and lowersections 5A, 5B of the oven (see FIG. 1). Electrical components asreferred to herein include any electrical, electronic, or associatedcomponents. The housing 831 comprises a front wall forming, in theillustrated embodiment, a control panel 551, a back wall 841, andopposing side walls 843. A chassis 845 extends between the side walls843 at a location forward of the back wall 841. The chassis 845 isdesirably secured by rivets or screws to respective side walls 843, tothe bottom wall of upper oven section 5A, and to the upper wall of loweroven section 5B. The control panel 551 is mounted on two slide rails 847having slide connections with the side walls 843 of the housing 831. Inthe illustrated embodiment, each slide connection between a rail 847 andrespective side wall 843 comprises two screws 849 extending throughhorizontal elongate slots 851 in the slide rail 847 and threaded into arespective side wall 843. The control panel 551 is connected to theslide rails 847 at the sides of the control panel by two upper screws857 and two lower screws 859.

As shown sequentially in FIGS. 29A-29C, the control panel 551 may beopened to provide convenient access to the various electrical componentsmounted within the housing 831. In a closed or upright position, asshown in FIG. 29A, the electrical components are concealed within thehousing 831. To open the control panel 551, the screws 849 holding theslide rails to side walls are loosened. Handles 863 on the control panel551 may then be used to pull the control panel forward, or in adirection away from the back wall 841, until the screws 849 through theslide rail slots 851 stop further forward movement of the slide rails847, as shown in FIG. 29B. The upper screws 857 connecting the controlpanel 551 to the slide rails 847 are then removed, allowing the controlpanel to be pivoted about an axis extending between the two lower screws859. In the open or hang-down position, as shown in FIG. 29C, theelectrical components mounted within the housing 831 are exposed forconvenient access and servicing. For example, the components mounted onthe back side of the control panel 551, including the main controller507 and associated components, are readily accessible. The componentsmounted on the side walls 843, including for example the main breakerswitches 525, high-limit thermostat 527 and USB host adapter 821, arealso readily accessible. Further, the components mounted on the chassis845, including for example the transformers 521, contactor device 531and blower speed/direction controller 509, are conveniently exposed andoriented in a position for convenient access. Without the chassis 845,electrical components would need to be mounted on, e.g., the back wall841 or the top wall of the lower section 5B.

The chassis 845 provides a vertical mounting surface forward of the backwall 841 and spaced relative to the control panel 551 in its closedposition to locate the electrical components mounted on the chassis in aposition where an operator may conveniently view, access and service thecomponents when the control panel is open. A primary mounting surface865 of the chassis 845 is located with respect to the control panel 551in its closed position to provide clearance between the electricalcomponents mounted on the chassis and back side of the control panel,and to position the components mounted on the chassis conveniently closeto the opening created when the control panel is open. In theillustrated embodiment, the control panel 551 is disposed at an anglefrom the vertical plane (e.g., 5 to 90 degrees, or more desirably 10 to70 degrees, or even more desirably 10-30 degrees) for convenience of useand best view of the operator input 505 (e.g., liquid crystal displaytouch screen). However, the control panel 551 may be disposed in agenerally vertical orientation. Whether the control panel 551 isdisposed at an angle or in a generally vertical orientation, thedistance between the control panel and the primary mounting surface 865of the chassis 845 is desirably between 2 and 15 in., more desirablybetween 4 and 12 in., and even more desirably between 5 and 9 in. Thedistance as used herein means the distance D in FIG. 28 as measured fromthe vertical centerline 867 of the front wall 551 in its closed positionand the vertical centerline 869 of the primary mounting surface 865 ofthe chassis 845. This spacing enables service personnel to convenientlyaccess components mounted on the primary mounting surface 865 of thechassis 845 with standard tools, such as a screwdriver with an 8 in.shaft and blade. The primary mounting surface 865 is desirablypositioned no further than 10 in. from the back side of the controlpanel 551 in its closed position to enable service personnel to usestandard tools. The spacing also allows for clearance between themounted components such that wires connecting the components are notpinched or bent and a minimum clearance is provided for flow of coolingair between the components. Other spacing arrangements than thosementioned above may be used.

The chassis 845 also serves to create a more efficient flow path forcooling air across the electrical components mounted within the housing831, the cooling flow path being defined by the space between thechassis and the front wall 551. The components are cooled by relativelycool air pulled by the cooling fan 541 through an inlet 871 in the sidewall 843. The chassis 845 is configured to decrease the area of the flowpath. Thus, less air is required to effectively cool the components, andone relatively small cooling fan 541 may be used rather than two or morefans. Desirably, air pulled by the cooling fan 541 does not pass throughthe space between the chassis 845 and the back wall 841.

FIGS. 30-32 illustrate another embodiment of a blower wheel, generallydesignated 121′, for circulating gas through the cooking chamber 11′,and a steam generation and water injection system, generally designated171′, for delivering water to the heated blower wheel 121′ fordispersion into the upper portion 53 a′ of the air conduit system 53.The blower wheel 121′ and the water injection system 171′ are similar inmany respects to the blower wheel 121 and water injection system 171described above, and corresponding parts are designated by thecorresponding reference numbers, plus a prime designator (′). In thisembodiment, an even number of blades 135′ are used to enhance balance ofthe blower wheel 121′, and fewer blades are used, creating more spacebetween the blades. The blades 135′ do not have water-dispersionformations for dispersing water into the cooking chamber like thewater-dispersion formations 151 of the blower wheel 121. Waterdispersion formations are not necessary in this embodiment because thewater injection system 171′ delivers water to a different location onthe blower wheel 121′. In this embodiment, as shown in FIGS. 30 and 32,the components of the injection system 171′ are mounted on the top wall107′ of the oven at a location where the injector 173′ extends from thetop wall down to a position for delivering water for impact against therotating and heated upper wheel member 131′ which, in this embodiment,comprises a circular plate (also designated 131′). Heating of the blowerwheel 121′ (and thus the upper wheel member 131′) is accomplished bycirculating hot gas (e.g., air) from the cooking chamber 11′ over thesurfaces of the blower wheel, which raises the temperature of the blowerwheel surfaces above the boiling point of water for steam generation. Byway of example, the injector may be spaced about 0.25 in. above thecircular plate 131′. As a result, water is injected onto the upwardfacing upper surface of the circular plate 131′, where much of the waterflashes to steam and is then dispersed into the cooking chamber 11′through the air conduit system 53. Water that does not flash to steamslides to the outside perimeter of the plate 131′, as a result of therotation of the plate, and is dispersed in the form of small dropletsacross the heating elements 71′ and onto the walls within the airconduit system 53, such as the side walls 47 or back wall 51. Waterdroplets that do not initially change to steam slide down the walls 47,51 to the bottom wall 45, where the water is then evaporated into steamvapor.

The embodiment including the blower wheel 121′ and the water injectionsystem 171′ provides several advantages, such as: more efficient steamgeneration; shielding of water droplets from contacting food product inthe cooking chamber 11; and less noise generation. The presentembodiment generates steam more efficiently because the water injectionsystem 171′ delivers water for impact against the upper surface of therotating upper wheel member 131′. The water remains in contact with theupper surface of the wheel member 131′ for a longer period of time thanit would if injected against the blades 135′, and the upper wheel member131′ has a relatively large surface area (approximately 155 squareinches in one embodiment). Thus, the upper wheel member 131′ impartsmore efficient heat transfer to the water, flashes the water to steammore effectively, and decreases the amount of water leaving the blowerwheel 121′ without flashing to steam. The present embodiment alsoshields water droplets from the water injection system 171′ fromentering the cooking chamber 11′ through the exhaust 69′ and undesirablyaffecting the cooking process. Introduction of water to the suction side121 a′ or even the output side 121 b′ of the blower wheel 121 may allowwater droplets that do not flash to steam to enter the cooking chamber11′ through the exhaust 69′ and contact the food product in the cookingchamber. In the present embodiment, water that does not flash to steamwhen it contacts the upper surface of the upper wheel member 131′ slidesto the outside perimeter of the plate and is dispersed onto the wallswithin the air conduit system 53, such as the side walls 47 or back wall51. Thus, water that does not flash to steam is moved away from theexhaust 69′ to avoid contact with the food product in the cookingchamber 11′. As shown in FIG. 32, water generally contacts the circularplate 131′ in the annular region 901, which has no holes through whichliquid can pass. The annular region 901 is bounded by the phantomcircular line designated 903 and by the outside perimeter of the plate.The phantom circular line 903 is concentric with the axis of rotation ofthe plate 131′ and has a radius less than the distance from the centerof the plate to the location on the plate over which the injector 173′is mounted. Further, the present embodiment results in less noisegeneration because the water impacting the circular plate 131′ createsless noise than if the water were impacting the rotating blades 135′ orwater-dispersion formations 151 (FIG. 3).

FIGS. 33-34 illustrate, in the lower section 5B of the oven 1, anotherembodiment of a blower wheel, generally designated 281′, for circulatinggas through the cooking chamber 225, and a water injection system,generally designated 351′, for delivering atomized water to the blowerwheel 281′ for dispersion into the air conduit system 271. The blowerwheel 281′ and the water injection system 351′ are similar in manyrespects to the blower wheel 281 and water injection system 351described above, and corresponding parts are designated by thecorresponding reference numbers, plus a prime designator (′). In thisembodiment, the blower wheel 281′ lacks the “squirrel cage” included onthe blower wheel 281. The water injection system of this embodimentincludes a quick-release connection between the supply line 389′ and theinjector 355′. A tab 903 at the end of the supply line 389′ is providedfor disconnecting the injector 355′, which has an 0-ring for creating afluid-tight seal between the injector and the supply line. In thisembodiment, the heating elements 311′ are located in different positionsin the air conduit system 271 below the bottom wall 229.

Having described the invention in detail, it will be apparent thatmodifications and variations are possible without departing from thescope of the invention defined in the appended claims. In this regard,it will be understood that an oven of this invention may have differentcooking chamber configurations. By way of example, the oven may haveonly one baking chamber 11 and no proofing chamber 225; or the oven mayhave two or more baking chambers 11 stacked one on top of another withno proofing chamber; or the oven may have one baking chamber and twoproofing chambers. Other combinations are possible.

When introducing elements of the present invention or the preferredembodiments(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

1-14. (canceled)
 15. An oven for cooking food, the oven comprising: acooking chamber for receiving the food, a recirculation conduit forcirculating gas from the cooking chamber back to the cooking chamber, ablower wheel in the recirculation conduit, a heater for heating the gas,and a water delivery system for delivering water to the blower wheel.16. An oven as set forth in claim 15, wherein the blower wheel islocated above the cooking chamber and mounted to rotate about agenerally vertical axis, the blower wheel including a plurality ofblades.